U.S. patent number 10,418,789 [Application Number 15/661,282] was granted by the patent office on 2019-09-17 for spark plug with a suppressor that is formed at low temperature.
This patent grant is currently assigned to Federal-Mogul Ignition LLC. The grantee listed for this patent is FEDERAL-MOGUL IGNITION LLC. Invention is credited to Keith Firstenberg, Shuwei Ma, Michael Saccoccia, William J. Walker, Jr..
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United States Patent |
10,418,789 |
Ma , et al. |
September 17, 2019 |
Spark plug with a suppressor that is formed at low temperature
Abstract
A spark plug suppressor and a method of producing a spark plug
suppressor from a suppressor precursor liquid that may be cured at
a temperature below 300.degree. C. The spark plug suppressor may
include particles or grains dispersed in a matrix of electrically
conducting material, electrically semiconducting material, or
electrically non-conducting material. The suppressor may include a
conductive glass seal component and a resistive suppressor
component. The resistive suppressor component may be at least
partially embedded in the glass seal component, and the glass seal
component may seal a center electrode of the spark plug, a terminal
of the spark plug, or both the center electrode and the
terminal.
Inventors: |
Ma; Shuwei (Ann Arbor, MI),
Firstenberg; Keith (Livonia, MI), Walker, Jr.; William
J. (Ann Arbor, MI), Saccoccia; Michael (Canton, MI) |
Applicant: |
Name |
City |
State |
Country |
Type |
FEDERAL-MOGUL IGNITION LLC |
Southfield |
MI |
US |
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Assignee: |
Federal-Mogul Ignition LLC
(Southfield, MI)
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Family
ID: |
61010660 |
Appl.
No.: |
15/661,282 |
Filed: |
July 27, 2017 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20180034247 A1 |
Feb 1, 2018 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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62367319 |
Jul 27, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01T
21/02 (20130101); H01T 13/41 (20130101) |
Current International
Class: |
H01T
13/41 (20060101); H01T 21/02 (20060101) |
Field of
Search: |
;313/134 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Maria, Jon-Paul et al., Cold Sintering: Current Status and
Prospects, J. Mater. Res., vol. 34, No. 17, p. 3205-3218 (Sep. 14,
2017). cited by applicant.
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Primary Examiner: Raabe; Christopher M
Attorney, Agent or Firm: Reising Ethington, P.C.
Parent Case Text
REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of U.S. Provisional Application
No. 62/367,319 filed Jul. 27, 2016, the contents of which are
hereby incorporated by reference in their entirety.
Claims
The invention claimed is:
1. A spark plug, comprising: a metallic shell having an axial bore;
an insulator having an axial bore and being disposed at least
partially within the axial bore of the metallic shell; a center
electrode being disposed at least partially within the axial bore
of the insulator; a ground electrode being attached to the metallic
shell; and a suppressor being arranged within the axial bore of the
insulator, wherein the suppressor is formed from a suppressor
precursor liquid that is cured at a temperature less than
300.degree. C. so that the cured suppressor precursor liquid
includes a network of particles or grains dispersed into a matrix
of electrically conducting material, electrically semiconducting
material, or electrically non-conducting material.
2. The spark plug of claim 1, wherein the suppressor includes first
and second conductive glass seal components and a resistive
suppressor component, wherein the resistive suppressor component is
at least partially embedded between the first and second glass seal
components and the first and second glass seal components seal the
center electrode, a terminal, or both the center electrode and the
terminal.
3. The spark plug of claim 1, wherein the particles or grains are
electrically conducting or electrically semiconducting and include
one or more of: carbon, copper, molybdenum, nickel, silicon,
titanium, tungsten, or compounds containing carbon, copper,
molybdenum, nickel, silicon, titanium, or tungsten.
4. The spark plug of claim 3, wherein the particles or grains are
in contact with one another in order to form an electrically
conductive pathway.
5. The spark plug of claim 3, wherein the matrix is comprised of an
electrically conducting material or an electrically semiconducting
material.
6. The spark plug of claim 3, wherein the matrix is comprised of an
electrically non-conducting material.
7. The spark plug of claim 1, wherein the particles or grains are
non-conductive and the matrix is comprised of an electrically
conducting material or an electrically semiconducting material.
8. The spark plug of claim 1, wherein the network includes a
network of siloxane (Si--O--Si) bonds resulting from a
polymerization of the suppressor precursor liquid.
9. The spark plug of claim 1, wherein the matrix of electrically
conducting material, electrically semiconducting material, or
electrically non-conducting material includes a geopolymer.
10. The spark plug of claim 9, wherein the matrix includes a
polymeric aluminosilicate (Si--O--Al) framework.
11. The spark plug of claim 1, wherein the suppressor has a
resistance between 1000 ohms and 15000 ohms.
12. A spark plug, comprising: a metallic shell having an axial
bore; an insulator having an axial bore and being disposed at least
partially within the axial bore of the metallic shell; a center
electrode being disposed at least partially within the axial bore
of the insulator; a ground electrode being attached to the metallic
shell; and a suppressor being arranged within the axial bore of the
insulator, wherein the suppressor is formed from a suppressor
precursor liquid, and the suppressor includes particles or grains
dispersed into a matrix of electrically conducting material,
electrically semiconducting material, or electrically
non-conducting material, wherein the particles or grains include
approximately 89-90 wt % calcined kaolin, 9-10 wt % calcium
hydroxide, and less than 1 wt % carbon black.
13. The spark plug of claim 12, wherein the particle size of the
calcined kaolin is less than about 45 microns.
14. A spark plug, comprising: a metallic shell having an axial
bore; an insulator having an axial bore and being disposed at least
partially within the axial bore of the metallic shell; a center
electrode being disposed at least partially within the axial bore
of the insulator; a terminal being disposed at least partially
within the axial bore of the insulator; a ground electrode being
attached to the metallic shell; and a suppressor being arranged
within the axial bore of the insulator between the center electrode
and the terminal, wherein the suppressor includes a conductive
glass seal component and a resistive suppressor component, wherein
the resistive suppressor component is adjacent to the glass seal
component and the glass seal component seals the center electrode,
the terminal, or both the center electrode and the terminal,
wherein the resistive suppressor component is formed from a
suppressor precursor liquid that is cured at a temperature less
than 300.degree. C., the suppressor precursor liquid including
precursor constituents in the form of electrically conducting
particles, electrically semiconducting particles, or electrically
non-conducting particles, wherein the precursor constituents are
mixed in a volatile organic compound (VOC) to form the suppressor
precursor liquid, wherein the resistive suppressor component
includes a network of the precursor constituents dispersed into a
matrix of electrically conducting material, electrically
semiconducting material, or electrically non-conducting
material.
15. A method of forming the suppressor of the spark plug of claim 1
within the axial bore of the spark plug insulator, the method
comprising the steps of: preparing the suppressor precursor liquid
by blending a solution and a powder mixture; adding the suppressor
precursor liquid into the axial bore of the spark plug insulator;
and curing the suppressor precursor liquid at a temperature below
300.degree. C.
16. The method of claim 15, wherein additional precursor
constituents are added to the suppressor precursor liquid in the
insulator axial bore and mixed in situ before curing.
17. The method of claim 15, wherein the step of adding the
suppressor precursor liquid includes metering and injecting the
precursor liquid into the axial bore of the spark plug
insulator.
18. The method of claim 15, wherein the ratio of the solution to
the powder mixture is between 1:1 and 1:3, inclusive.
19. The method of claim 15, wherein the solution includes urea or
sodium hydroxide mixed with sodium silicate.
20. The method of claim 15, wherein the curing step includes a
hydrolysis, condensation, and polymerization sol-gel reaction
method.
Description
FIELD
The invention generally relates to spark plug suppressors and
methods for making spark plug suppressors.
BACKGROUND
Spark plug suppressors can help suppress or reduce electromagnetic
interference (EMI) and/or radio frequency interference (RFI), which
may be by-products of an ignition spark when the spark plug is used
in an internal combustion engine. The EMI and/or RFI may interact
with engine control systems and/or other on-board electronic
devices, so reducing the EMI and/or RFI may be desirable in some
instances. Additionally, spark plug suppressors may help seal one
or more spark plug components such as the center electrode,
terminal, or both within an axial bore of the insulator.
SUMMARY
According to one embodiment, there is provided a spark plug
comprising a metallic shell having an axial bore, an insulator
having an axial bore and being disposed at least partially within
the axial bore of the metallic shell, a center electrode being
disposed at least partially within the axial bore of the insulator,
a ground electrode being attached to the metallic shell, and a
suppressor being arranged within the axial bore of the insulator.
The suppressor is formed from a suppressor precursor liquid, and
the suppressor includes particles or grains dispersed into a matrix
of electrically conducting material, electrically semiconducting
material, or electrically non-conducting material.
According to another embodiment, there is provided a spark plug
comprising a metallic shell having an axial bore, an insulator
having an axial bore and being disposed at least partially within
the axial bore of the metallic shell, a center electrode being
disposed at least partially within the axial bore of the insulator,
a terminal being disposed at least partially within the axial bore
of the insulator, a ground electrode being attached to the metallic
shell, and a suppressor being arranged within the axial bore of the
insulator. The suppressor includes a conductive glass seal
component and a resistive suppressor component. The resistive
suppressor component is at least partially embedded in the glass
seal component and the glass seal component seals the center
electrode, the terminal, or both the center electrode and the
terminal. The resistive suppressor component is formed from a
suppressor precursor liquid, and the suppressor precursor liquid
includes precursor constituents in the form of electrically
conducting particles, electrically semiconducting particles, or
electrically non-conducting particles. The precursor constituents
are mixed in a volatile organic compound (VOC) to form the
suppressor precursor liquid. The resistive suppressor component
includes the precursor constituents dispersed into a matrix of
electrically conducting material, electrically semiconducting
material, or electrically non-conducting material.
According to another embodiment, there is provided a method of
forming a suppressor within an axial bore of a spark plug
insulator. The method comprises the steps of preparing a suppressor
precursor liquid, adding the suppressor precursor liquid into the
axial bore of the spark plug insulator, and curing the suppressor
precursor liquid at a temperature below 300.degree. C.
DRAWINGS
Preferred exemplary embodiments will hereinafter be described in
conjunction with the appended drawings, wherein like designations
denote like elements, and wherein:
FIG. 1 is a cross-sectional view of a spark plug with an exemplary
spark plug suppressor; and
FIG. 2 is a flow chart depicting an exemplary method for forming
the spark plug suppressor of FIG. 1.
DESCRIPTION
The present application describes a suppressor for a spark plug and
a method of making the same, where the suppressor is designed to
reduce the amount of electromagnetic interference (EMI) produced by
the spark plug when it is used in an engine. More specifically, a
suppressor or suppressor seal or noise suppressor, as it is
sometimes called, minimizes EMI by acting as a resistor within an
insulator bore and absorbing interfering electromagnetic waves.
According to one embodiment of forming the present suppressor, one
or more precursor constituents are prepared into a liquid state,
are poured, injected, or otherwise added into an axial bore of a
spark plug insulator, are mixed with any remaining precursor
constituents, and are then cured and solidified at a relatively low
curing temperature (e.g., below 300.degree. Celsius).
Unlike traditional methods that utilize powder and other non-liquid
precursor constituents, the present method may enjoy certain
manufacturing benefits. One potential benefit of the present method
pertains to better consistency and uniformity among different
suppressor batches, as well as within a particular suppressor
batch. Liquid precursors can use higher shear to achieve better
homogenization of the constituents as opposed to a glass powder
mixture, and a liquid can also be metered and fed into the bore of
an insulator with good accuracy. Furthermore, the precursor
constituents can be prepared outside of the spark plug insulator in
large batches, such as in a liquid slurry or paste, further
enabling the production of larger uniform batch quantities. Another
potential benefit is that a liquid material does not generate the
same dust as a powder. This improves manufacturing conditions and
also reduces the risk of cross contamination during production.
Also, the method described herein utilizes a relatively low
temperature curing process (e.g., below 300.degree. C.) which in
turn reduces energy costs and expensive manufacturing equipment.
Because the precursor constituents are already prepared in a liquid
form and therefore do not need to be melted before being hardened,
traditional melting and/or firing steps can be eliminated.
The spark plug suppressor and corresponding manufacturing method
set forth in this description can be used with a wide variety of
spark plugs and other ignition devices including automotive spark
plugs, diesel glow plugs, industrial plugs, aviation igniters, or
any other device that is used to ignite an air/fuel mixture in an
engine. This includes spark plugs used in automotive internal
combustion engines equipped to provide gasoline direct injection
(GDI), turbo- or super-charged engines, engines operating under
lean burning strategies, engines operating under fuel efficient
strategies, engines operating under reduced emission strategies, or
a combination of these. As used herein, the terms axial, radial,
and circumferential describe directions with respect to the
generally cylindrical shape of the spark plug of FIG. 1 and refer
to a center axis A of the spark plug 10, unless otherwise
specified.
Referring to FIG. 1, a spark plug 10 includes a center electrode
(CE) base or body 12, an insulator 14, a metallic shell 16, a
ground electrode (GE) base or body 18, a terminal 20, and a
suppressor 22.
The CE body 12 is generally disposed within an axial bore 40 of the
insulator 14, and has a sealed end portion 32 and a firing end
portion 34 exposed outside of the insulator at a firing end of the
spark plug 10. The sealed end portion 32 is typically enlarged, in
terms of its diameter, so that it rests on an interior shoulder 46
formed in the insulator bore 40. The firing end portion 34 is
located on the opposite axial end of the CE body 12 and usually
protrudes out of the insulator bore 40 so that it is exposed to a
spark gap, as shown. In one example, the CE body 12 is made of a
nickel-based alloy material that serves as an external or cladding
portion of the body, and includes a copper or copper-based alloy
material that serves as an internal core of the body (not shown)
for managing heat within the CE body. Of course, other materials
and configurations are possible including a non-copper cored CE
body made of a single material. The CE body 12 may or may not
include a separate firing tip, pad or piece 36 made of one or more
precious metal-based alloys, such as those made of platinum,
iridium, ruthenium, palladium, rhodium or a combination thereof.
The aforementioned features and possibilities apply to the GE body
18 as well; thus a separate description has been omitted.
The insulator 14 is generally disposed within an axial bore 50 of
the metallic shell 16, and has a terminal portion 42 and a nose
portion 44 exposed outside of the shell at the firing end of the
spark plug 10. Along the axial length of the insulator 14, between
the terminal portion 42 and the nose portion 44, the insulator
axial bore 40 may include different sections or segments of varying
internal diameter. For example, a first interior shoulder 46 is
formed so that the enlarged sealed end portion 32 of the CE body
can rest upon and be sealed against the insulator. The insulator
bore 40 may include other interior shoulders, tapers and
configurations and does not have to be a straight cylindrical bore,
as shown in sections of FIG. 1. The insulator 14 is made of a rigid
electrically insulating material, such as a ceramic material, that
electrically isolates the CE body 12 from the metallic shell
16.
The metallic shell 16 surrounds portions of the insulator 14 and
includes at least one ground electrode attached at the front end of
the spark plug. While the ground electrode 18 is depicted in the
traditional J-gap configuration, it will be appreciated that spark
plug 10 may have a single electrode, multiple ground electrodes, or
an annular ground electrode, or any other known configuration can
be substituted depending upon the intended application of the spark
plug.
The suppressor 22 is located within the insulator axial bore 40.
The suppressor 22 provides an electrical path through the center
wire assembly from the terminal 20 to the center electrode base 12
at the sealed end portion 32. Spark plugs having such features are
sometimes termed resistor spark plugs or suppressor spark plugs.
The suppressor 22 serves to suppress or reduce electromagnetic
energy, including electromagnetic interference (EMI) and radio
frequency interference (RFI), caused as a by-product of an ignition
spark. EMI and RFI can affect engine control systems and other
on-board electronic devices, so it is desirable to reduce these
types of interferences. Suppressors are also utilized to combat the
high temperatures and pressures exerted on a spark plug when
operating in the combustion chamber. The suppressor component 22
acts as a strong seal to hold the components within the insulator
bore 40, such as the center electrode 12, while also minimizing gas
leakage through the longitudinal length of the insulator.
The suppressor 22 may be a single, homogeneous suppressor
component, or it may be segmented into separate suppressor
components, such as conductive and/or resistive segment(s). FIG. 1
illustrates a segmented exemplary design wherein there are several
distinctive suppressor components and/or layers stacked axially
within the insulator axial bore 40. A resistive suppressor
component is designated as element 60, a first conductive glass
seal component is designated as element 62, and a second conductive
glass seal component is designated as element 64. The resistive
suppressor component 60 may have a resistivity between 1 k.OMEGA.
and 15 k.OMEGA., for example. In such design, the conductive layers
62, 64 provide a transition between the metallic terminal 20 and
the resistive suppressor component 60 and the center electrode body
12, as component 60 may not seal well to metallic pieces 20 and 12.
The suppressor component 22 may form a hermetic seal in the
internal bore 40 of the insulator and bond to the lower end of
terminal 20 and/or the sealed end portion 32 of the CE. With
respect to FIG. 1, this bonding is found between glass seal
component 62 and terminal 20 and/or between glass seal component 64
and sealed end portion 32. It will be appreciated that the
configuration and distributions in FIG. 1 of resistive and
conductive segments is exemplary, and suppressor component 22 may
exist in a variety of different resistive and conductive
configurations and distributions. For instance, suppressor 22 may
include different numbers and/or sequences of conductive and
resistive components, and is not limited to one-part or three-part
embodiments. Moreover, suppressor component 22 may be used in
conjunction with a variety of center wire components, including
those elements that are known in the art but not illustrated in
FIG. 1, such as a spring or push pin, to cite a few examples.
Precursor constituents for the suppressor component 22 may include
electrically conductive particles or grains, electrically
semiconductive particles or grains, electrically non-conductive
particles or grains, or any combination of these. Precursor
constituents may be prepared through the addition of solvents, such
as volatile organic compounds (VOCs). Examples of electrically
non-conductive particles may include one or more of: alumina,
silica, zirconia, titania, silicate glass, alumino-silicate glass,
and boro-silicate glass. Examples of electrically conductive
particles or grains may include one or more of: carbon, copper,
molybdenum, nickel, silicon, titanium, tungsten, or any of these
compounded with oxygen, carbon or other suitable element (such as
tungsten oxide, silicon carbide and moly-disilicide). Other
appropriate electrically conductive, semiconductive, and/or
nonconductive materials may include geopolymers (also known as
Inorganic aluminosilicate polymers and consisting of a polymeric
Si--O--Al framework). In the segmented or multi-component
suppressor design, these precursor constituents may be used to form
the resistive elements and/or the conductive elements, but are
particularly suitable for forming the resistive elements.
According to a first non-limiting example, a dry powder mixture may
be prepared having approximately 85-90 wt % calcined kaolin with
particle sizes of less than about 45 microns, 5-15 wt % calcium
hydroxide, and less than 1 wt % carbon black. A solution is
prepared by mixing 5-15% of a 30% sodium hydroxide solution and
85-90% "N brand" sodium silicate. The solution and the powder
mixture are blended in a ratio of between 1:1 and 1:3 to produce a
"suppressor precursor liquid". It will be understood by one skilled
in the art that the amount of carbon or graphite can be varied in
order to produce the desired electrical resistance of the seal.
According to a second non-limiting example, a powder may be
prepared having calcined kaolin and less than 0.5% carbon black. A
liquid is then prepared, as in the first example, but substituting
Urea for sodium hydroxide. The two can be mixed in a ratio between
1:1 and 1:3. The ratio of powder to liquid can control the working
time of the mixture its viscosity and/or other characteristics. A
larger ratio of the liquid will result in a shorter working time
before the viscosity increases out of the usable range. Again, the
aforementioned examples are non-limiting and simply provide some
possibilities in terms of the suppressor component; other
possibilities certainly exist.
Turning next to FIG. 2, an exemplary method of forming a spark plug
suppressor 22 is now described in more detail. This method is
applicable to any or all of suppressor subcomponents 60, 62 and/or
64.
According to a method as depicted in FIG. 2, the suppressor 22 is
formed from a series of steps. Beginning with step 102, one or more
constituents are joined, mixed or otherwise introduced to form a
suppressor precursor liquid. "Suppressor precursor liquid," as used
herein, means a liquid or semi-liquid mixture of suppressor
precursor material and may be provided in the form of a liquid,
paste, slurry or other substance having a similar consistency. The
suppressor precursor liquid is made of at least one precursor
constituent, which may be blended, mixed and/or prepared before
being inserted into the insulator axial bore 40. Where more than
one precursor constituent exists, all of the precursor constituents
may be blended or mixed together prior to being introduced into the
insulator axial bore 40, all of the precursor constituents may be
prepared separately and blended or mixed together after being added
to the insulator axial bore 40 (in situ), or a mix of the two
options may be used.
In step 104, the suppressor precursor liquid(s) are added or
introduced into the axial bore of the insulator. Adding may be done
by pouring, injecting, metering, or any other way of transferring
the suppressor precursor liquid into the insulator axial bore 40.
In the example where the components of the suppressor precursor
liquid are blended or mixed before insertion into bore 40, the
consistency of the precursor liquid may be somewhat akin to a
viscous paste. For instance, the precursor liquid may have a
viscosity of approximately 5 to 10 Pascal seconds, but other
viscosities may be used instead. Step 104 may inject the somewhat
viscous suppressor precursor liquid using any suitable method or
technique that cleanly introduces the substance into the insulator
axial bore, such as by using a syringe, funnel or dropper, to cite
just a few of the possibilities. In the example where the
components are blended within the axial bore 40 (in situ), the
suppressor precursor liquid may be slightly less viscous, in which
case, step 104 may meter out the liquid using the same or other
techniques.
In some embodiments, not all precursor constituents were mixed
together in step 102. In such cases, the remaining precursor
constituents may be added to the suppressor precursor liquid in the
insulator bore in step 106. For example, as a modification to the
first and second non-limiting examples described above, the powder
could be mixed with water to form a precursor paste, with the
liquid solution added later, just before use. Other embodiments are
certainly possible.
In step 108, the suppressor constituents are cured at a relatively
low curing temperature below 300.degree. C. to form a solid
suppressor component 22. Once cured, the suppressor component 22
may form a hermetic seal in the internal bore 40 and bond to the
lower end of terminal 42 and/or the sealed end portion 32 of the
CE.
There are a variety of ways to cure the suppressor seal
constituent(s) at a relatively low curing temperature. A few of the
non-limiting exemplary embodiments are discussed herein. In one
embodiment, the suppressor component 22 cures because of the
reaction of one or more alkali silicates with a powder from the
group comprising alumina, silica, silicates and alumino-silicates.
This is commonly referred to as the alkali-silica reaction (ASR).
In other embodiments, hydrolysis, condensation and/or
polymerization methods are used. A sol-gel reaction, for example,
may utilize all three. The chemical reaction that causes the
suppressor component 22 to cure in a sol-gel reaction is based upon
the hydrolysis and condensation of silicon alkoxide. The hydrolysis
(a) and condensation (b) of silicon alkoxide is illustrated below:
(a) Si--OR+H.sub.2O.fwdarw.Si--OH+ROH (b)
Si--OH+Si--OR.fwdarw.Si--O--Si+ROH
Si--OH+Si--OH.fwdarw.Si--O--Si+H.sub.2O
Although the sol-gel condensation step may require some input of
energy and/or a drying step may follow the condensation step in
order to solidify the gel into a lattice or matrix, the input is
well below the energy required in traditional firing methods. For
instance, fired in suppressor seals (FISS) usually have to be
melted at temperatures of about 875.degree. C.-900.degree. C. in
order to form the suppressors in the insulator bore. This process
is much different than that described here, which does not require
such high temperature furnaces, etc.
Another chemical reaction that may be used in the curing of the
suppressor component 22 is the hydrolysis of ethyl silicate,
tetra-ethyl ortho-silicate or other alkyl silicates. For example,
and similar to above,
Si(OC.sub.2H.sub.2)+H.sub.2O.fwdarw.Si(OH).sub.4+C.sub.2H.sub.3OH.
This may occur as part of the sol-gel process.
It is also possible to use a thermoset ceramic or polymer material,
such as a one-part epoxy resin, which stays as a liquid precursor
until some input energy (usually heat, but could also be light,
such as UV light) is added to initiate the reaction. It is also
possible to use a two-part epoxy, where one part is a liquid until
it is mixed with an activator to cause a polymerization reaction.
Skilled artisans will appreciate that one part materials must
remain protected from the initiator energy or they may solidify
prematurely, whereas two part materials are each stable when kept
separate, but once mixed, will remain a liquid until an initiator
is added, whether heat or UV or other. Two part epoxy materials
generally begin polymerizing as soon as an "activator" solution is
added to the base, and can take from a few seconds to several
hours. Sometimes these are assisted by the addition of heat, but
are usually below 100.degree. C., as too much heat can damage the
polymerization reaction. Oftentimes curing will happen without any
assistance once the activator is added. Other suitable curing
methods and techniques are certainly possible.
The electrically conductive, semiconductive, and/or nonconductive
materials may form a matrix or lattice once cured. It is possible
to have electrically conducting or electrically semiconducting
particles or grains dispersed into a matrix of non-conducting
material. It is possible to have electrically non-conducting
particles or grains dispersed into a matrix of conducting or
semi-conducting material. It is also possible to have electrically
conducting or electrically semiconducting particles or grains
dispersed into a matrix of electrically conducting or
semiconducting material. According to one example, a matrix is
formed containing dispersed particles or grains of conducting or
semiconducting material, where the dispersed particles are in
contact with one another in order to form an electrically
conductive pathway. The extent to which the particles form
electrically conductive pathways controls the overall electrical
resistance of the suppressor component.
The desired electrical resistivity of the suppressor component 22
is controlled by regulating the precursor constituents in the
matrix. The suppressor component 22 may have an electrical
resistance between 1000 and 15000 Ohms.
It is to be understood that the foregoing description is not a
definition of the invention, but is a description of one or more
preferred exemplary embodiments of the invention. The invention is
not limited to the particular embodiment(s) disclosed herein, but
rather is defined solely by the claims below. Furthermore, the
statements contained in the foregoing description relate to
particular embodiments and are not to be construed as limitations
on the scope of the invention or on the definition of terms used in
the claims, except where a term or phrase is expressly defined
above. Various other embodiments and various changes and
modifications to the disclosed embodiment(s) will become apparent
to those skilled in the art. All such other embodiments, changes,
and modifications are intended to come within the scope of the
appended claims
As used in this specification and claims, the terms "for example,"
"e.g.," "for instance," "such as," and "like," and the verbs
"comprising," "having," "including," and their other verb forms,
when used in conjunction with a listing of one or more components
or other items, are each to be construed as open-ended, meaning
that that the listing is not to be considered as excluding other,
additional components or items. Other terms are to be construed
using their broadest reasonable meaning unless they are used in a
context that requires a different interpretation.
* * * * *